The present invention relates to a film advance mechanism which may form, for example, part of a bag making and filling apparatus for snack foods such as potato crisps.
Known film advance mechanisms involve accurately positioning rubber wheels or the like to bear against opposite sides of a tubular film support over which a tubular film is conveyed. Careful control of the pressure of engagement of the rubber wheels is important because they must grip the film sufficiently to slide it over the film support but must not press it too firmly against the film support to generate excessive friction. The wheels require frequent adjustment to keep them in position and are susceptible to any eccentricities in the bearings, to any misalignment of the support, or a support with non-parallel side walls.
It is an object of the present invention to provide a film advance mechanism which is self-adjusting and able to cope with misalignments.